Method for establishing a multi-link access between a local network and a remote network, and corresponding appliance

ABSTRACT

The invention enables the different access links between a local network and a remote network to be used in a common and transparent manner. The invention is based on the use of various IP tunnels using the different access links between an appliance on the local network of the user and an appliance on the remote network. Said tunnels are embodied as a single link providing access to the remote network.

This application claims the benefit, under 35 U.S.C. § 365 ofInternational Application PCT/EP2006/061692, filed Nov. 2, 2006, whichwas published in accordance with PCT Article 21(2) on Nov. 2, 2006 inFrench and which claims the benefit of French patent application No.0551066, filed Apr. 25, 2005.

1. TECHNICAL FIELD

This invention relates to Internet access for a user and morespecifically to the common operation of several access links between thehome and the network.

2. TECHNOLOGICAL BACKGROUND

Connection to a remote network, for example Internet, from the usernetwork, illustrated by FIG. 1, is traditionally achieved with the helpof an access device, generally called modem, referenced 1.8, whether iteffectively concerns a modulation demodulation appliance of digitalsignals on an analogue link or by extension another technology. Thismodem enables a link, referenced 1.5, to be established between thisdevice and a peer, referenced 1.4, within the network of an accessprovider, referenced 1.3. The peer being called a NAS (Network AccessServer). The IP communications between the user network and the remotenetwork, herein the Internet network referenced 1.2, are directed viathe modem and pass through the link. The IP packets meant for purposesother than the user's internal network, referenced 1.7, are routed viathe modem, the incoming packets are those routed from the remote networkvia the NAS then the modem on the user network. A client, referenced1.9, within the user's house, referenced 1.6, can therefore access aserver, referenced 1.1, available on the Internet.

The development of connection techniques to a remote network leads tothe existence of multiples operators offering this connection by meansof various technical solutions. It is therefore now possible for a userto have several accesses to a remote network. The user can, forinstance, have at his disposal access through a standard modem, known asPSTN, and higher speed access offered by his cable operator wherein liesan offer comprising Internet access, telephony over IP and televisionvia an ADSL type connection. This type of user network is illustrated inFIG. 2. In this figure, we can see the home of a user, referenced 2.6,hosting the user network, referenced 2.7. A client, for example apersonal computer, referenced 2.9 is connected to this network 2.7. Afirst modem, referenced 2.8, for example a PSTN modem, offers a firstaccess via a first access provider, referenced 2.3. This access provider2.3 hosts an access device to its network referenced 2.4 enabling themodem 2.8 to open a link referenced 2.5. This access provider thereforeoffers access via its NAS 2.4 to the remote network, typically Internet,referenced 2.2. The user possesses a second modem, referenced 2.10,enabling him to access the Internet via a similar access offered by asecond provider, referenced 2.12. The manner in which the client 2.9will access a server, referenced 2.1, over the Internet and the accessused will be determined by configuration of the routing tables of theclient.

Solutions allowing common operation of several accesses do exist. It ispossible for instance to couple a mono-directional access via satelliteand a low-speed PSTN connection. In this case, the low-speed connectionis used for sending queries while the high-speed downstream connectionis used for the responses. The low-speed connection is thereforededicated to the outgoing traffic, while the high-speed connection isdedicated to the incoming traffic.

There are also other solutions that make it possible to share differentaccess links within the network. In this case the choice of the accessused is made at the IP connection level. A given IP connection will beestablished via one of the accesses. In this case a query and itsresponse must use the same access.

However, a common operation of the different access links in atransparent manner, making it possible to use the different accesseseach of which has its own bandwidth, as a single access possessing abandwidth equal to the sum of the bandwidths of the different accesslinks is not possible.

3. SUMMARY OF THE INVENTION

The invention enables the different access links between a local networkand a remote network to be used in a common and transparent manner. Theinvention is based on the use of various IP tunnels using the differentaccess links between an appliance on the local network of the user andan appliance on the remote network. Said tunnels are embodied as asingle link providing access to the remote network.

The invention relates to a method of connecting a local communicationnetwork through digital data packets to a remote network comprising atleast the following steps:

-   -   A step relating to the opening of a first connection between a        modem connected to the local network and the remote network via        a first access network,    -   A step relating to the opening of at least a second connection        between the said modem and the remote network via a second        access network,    -   A step wherein each of the connections thus opened, establish a        corresponding communication tunnel between the modem and an        appliance connected to the remote network called Gateway using        the said connection, and    -   A step wherein for each digital data packet exchanged between        the local network and the remote network, as much through the        modem as through the gateway, a choice of the tunnel used for        routing the packet.

According to a specific embodiment, the method furthermore comprises astep relating to the allocation of an address to the modem by thegateway.

According to a specific embodiment, the method furthermore comprises theopening of a control link between the modem and the gateway using one ofthe connections opened.

According to a specific embodiment, the choice step is carried outaccording to parameters specific to each tunnel.

According to a specific embodiment, the parameters specific to eachtunnel used in the choice step include the instantaneous usage rate ofeach connection.

The invention also relates to a communication appliance between a localcommunication network through digital data packets to a remote networkcomprising a plurality of means of opening of connections between thelocal network and the remote network, characterized in that itfurthermore comprises means to establish, for each connection opened, atunnel between itself and an appliance connected to the remote network,called gateway, using the connection and for each data packet that itrelays between the local network and the remote network, means of choiceof the tunnel used to relay the said packet.

According to one particular embodiment, the communication appliancefurthermore comprises the management means of an address on the networkallocated by the said gateway.

According to one particular embodiment, the communication appliancefurthermore comprises management means for a control link between itselfand the gateway using one of the connections opened.

The invention also relates to an appliance for relaying data packetsthat can be connected to a communication network through digital datapackets characterized in that it comprises a means of managing aplurality of tunnels between itself and a remote appliance over thenetwork and for each data packet that it relays towards the remoteappliance, means of choice of the tunnel used for relaying the saidpacket.

According to one particular embodiment, the relay appliance furthermorecomprises means of allocation of an address to the remote appliance.

According to one particular embodiment, the relay appliance furthermorecomprises means of management of a control link between itself and theremote appliance.

According to one particular embodiment, the means of choice of thetunnel are carried out according to parameters specific to each tunnel.

According to one particular embodiment, the parameters specific to eachtunnel used by the means of choice include the instantaneous usage rateof each connection opened between the remote appliance and the networkand sent by the remote appliance.

4. LIST OF DRAWINGS

The invention will be better understood, and other specific features andadvantages will emerge from reading the following description, thedescription making reference to the annexed drawings wherein:

FIG. 1, represents the known diagram of the connection of a localnetwork to the Internet,

FIG. 2, represents the known diagram of the connection of a localnetwork to the Internet via two different accesses,

FIG. 3 represents the connection diagram of a local network to theInternet according to one embodiment of the invention,

FIG. 4 represents the logical diagram of the connexion said to bemulti-link according to one embodiment of the invention,

FIG. 5 represents the software architecture diagram of one embodiment ofthe invention, and

FIG. 6 represents the different data packets as well as the addressesused in one embodiment of the invention.

5. DETAILED DESCRIPTION OF THE INVENTION

A detailed description of the invention as well as an embodiment willnow be described.

The routing rules used by IP networks are such that in a configurationsuch as the one described in FIG. 2, the response to a query passingthrough one of the access links will necessarily use the same linkduring its return. In fact, each access provider allocates an address ora set of addresses to the user. Two ways of managing the addressing ofthe user appliances within his local network can be used. A firstsolution consists in direct addressing. In this case the access providersupplies addresses within its own addressing space to the differentappliances of the local network. The said appliances will therefore beembodied, at the IP addressing level, as appliances that are an integralpart of the access provider's network. This type of addressing is stillcommonplace in the case of the connection of a single appliance to theInternet. In order to offer more flexibility to the user, it is possibleto use an address translation technique at the modem level. This enableshim to connect as many appliances as he wishes to the domestic networkwithout, for all this, requiring as many addresses within the addressingspace of its access provider. The modem is seen here as a router servingas an access gateway. This technique, which is well known under the nameof NAT (Network Address Translation), makes it possible to freelyorganize the addressing space of the user network. In this case, anaddress is allocated to the modem on the local network coherent withthis private addressing space. However, when the connection is set upwith the access provider, a second IP address is allocated to the modemby the access provider within its own addressing space. The modemtherefore has two addresses, one for the interface connecting it to thedomestic network and the other for the interface connecting it to theaccess provider. When a client of the home network sends a packet to theremote network, the source address of the packet will be translated bythe modem that replaces it with its own address within the provider'snetwork. The modem therefore appears as the source appliance of all thepackets originating from the local network and meant for the remotenetwork. The modem keeps the trace of the translations made in such amanner as to be able to send back over the internal network the packetsconstituting the responses that it receives. Here, it replaces its ownaddress used in the address of the destination of the packets by theaddress on the user network of the client.

Owing to this, a query originating from the local network will be seenon the remote network as having its origin in the access provider'snetwork used for sending the query. The response to this query willtherefore be directed towards this access provider and can reach theclient only via the network of this provider. The access used for thisquery therefore governs the access used for the response. We cantherefore see that though it is possible to use several accesses betweena local network and a remote network, the choice of the access can onlybe made at the session level.

If one wishes to share several access links between a local network anda remote network, in a transparent manner and in such a fashion as to beable to make full use of all the available bandwidth, one must design amechanism making it possible to route the traffic at the packet level.

An embodiment of such a mechanism will now be described. Thearchitecture of this example is illustrated in FIG. 3. The space of auser, referenced 3.6, comprises a local network, referenced 3.7, atleast one client referenced 3.15. The user possesses several accesseswith, for instance, different access providers. The figure illustratestwo access providers, IAP 1 and IAP 2, referenced 3.3 and 3.12. Each ofthese providers has an access server to the remote network at itsdisposal. These network access servers (NAS for Network Access Server)NAS 1 and NAS 2 referenced 3.4 and 3.13, grant access to the remotenetwork, in this case the Internet referenced 3.2. The remote network3.2 hosts servers such as the server referenced 3.1 in the figure. Wetherefore seek to establish a connection between the client 3.15 and theserver 3.1 by jointly using the accesses offered by both accessproviders. The principle illustrated here for two providers can bedirectly generalized to more than two providers. The embodiment of theinvention is based on the one hand on a relay appliance called amulti-link gateway, referenced 3.14, and connected to the remote network3.2 and on the other hand on a multi-link modem, referenced 2.9,directly controlling the interfaces, referenced 3.8 and 3.10, enablingthe opening of an access to each access provider. The embodiment of theinvention is based on the establishment of IP tunnels between themulti-link modem and the multi-link gateway. The multi-link modem, likethe multi-link gateway, chooses the tunnel and therefore the access usedfor each data packet exchanged between the local network and the remotenetwork. This choice may be dependent on various parameters such as thebandwidth of each access, the type of traffic in which the packetparticipates, instantaneous statistics of use of each link, the transfertime of the packet (round trip delay) or any other relevant parameter.In this manner, the different tunnels established will be jointly usedin such a manner as to form what we call a multi-link.

FIG. 4 illustrates the logical links existing between the multi-linkgateway, referenced 4.1 and the multi-link modem, referenced 4.2. Afirst connection, referenced 4.3, is initiated, for example, by themulti-link modem in an initialization phase. This connection isdedicated to the exchanges between the multi-link gateway and themulti-link modem for the purpose of controlling the functioning of themulti-link. Subsequently, one connection per access, referenced 4.4,4.5, 4.6 and 4.7, is identified. An IP tunnel is constituted on each ofthese connections. The IP tunnels can for instance be constituted byusing the GRE protocol (Generic Routing Encapsulation) defined in therequest for comments RFC2784 of the IETF (Internet Engineering TaskForce). Each tunnel is established on the one hand between the gatewayin its IP address on the remote network, called @IPP in the figure andthe address allocated to the modem by each IAP, at the time ofestablishing the connection, called @IPMi, i being the access number.

During an initialization phase, the multi-link modem will begin byopening the connections of each of the interfaces with the remotenetwork. The opening of this connection is done with the help of knownprotocols like for example PPP (Point to Point Protocol) used forexample for standard PSTN, DHCP connections (Dynamic Host ControlProtocol) used over Ethernet, PPPoE (PPP over Ethernet) used for examplefor ADSL connections, or any other type of protocol enabling theestablishment of a connection. In a general manner, at the time ofestablishing the connection, an IP address will be allocated by theaccess provider to the connecting appliance. This IP address willtherefore be supplied to the multi-link modem which will be equippedwith one address per access, each address corresponding to the interfaceconnecting it to the network.

Once the different connections are open, the modem will indifferentlyuse any one of them for establishing the control connection with themulti-link gateway. The manner in which the modem recognizes the addressof the gateway is indifferent, it can for instance involve a manualconfiguration or a parameter sent by one of the access providers at thetime of establishing one of the connections.

Once this connection or control link is established, the multi-link mustbe established. This establishment can begin with a possibleauthentication phase between the gateway and the modem. Subsequently themodem will declare the various connections established as well as theaddress that was allocated to it for each connection.

Then, in the same manner as an NAS allocates an IP address in its ownaddressing space to a connecting appliance, the multi-link gateway willallocate an IP address to the multi-link modem in its own addressingspace. This address is called @IPMV, as the virtual IP address of themodem. The flow of the packets exchanged between the client and a serverof the remote network through the multi-link will be described fartherahead.

The appliances or clients of the local network must have their routingtable indicating the modem as the gateway to the remote network to usethe resources of the multi-link. The existence of the multi-link doesnot in any manner alter the possibility of using the different accessesindependently of the multi-link by configuration of the routing on themodem.

Once the multi-link has been established, it is advisable to retain thecontrol connection. Indeed, this makes it possible to deal with anymodification of the number of access between the local network and theremote network. When, for instance, one connection falls, the modemshould inform the gateway to no longer use this access for the trafficcoming from the remote network to the local network. It is also possibleto add a new access that would be available to the multi-link. Thecontrol link can also be used for communication between the gateway andthe modem of information on the different links, information that may beuseful for the policy of choosing one of the accesses during the routingof a packet.

An interesting development of this possibility of making the multi-linkevolve dynamically over time with regard to its composition is theprocessing of roaming. In fact, a roaming appliance during its roamingwill see the networks to which it can have access change. As long as atleast one connection remains operational, the multi-link remainsfunctional. The loss of the connection to a network results in thewithdrawal of this link from the multi-link, while the connection to anew network that has become accessible results in its addition in themulti-link. In this fashion a roaming appliance can migrate from onenetwork to another while all the while retaining its connection with theremote networks via the multi-link, the changes of access remainingtransparent for the applications.

FIG. 5 illustrates the software architecture diagram of the embodimentof the invention. In it, we can see a client, referenced 5.4, having astandard software architecture made up of a physical layer, referenced5.44, that could be Ethernet or a wireless network 802.11 for example, alink layer, referenced 5.43, the IP layer referenced 5.42, above it theTCP transport layer referenced 5.41 and an application layer referenced5.40. At the other end of the system, the server, referenced 5.1, alsopossesses the same standard software architecture, the physical layer,referenced 5.14, the link layer, referenced 5.13, the IP layer,referenced 5.12, the TCP layer, referenced 5.11 and the applicationlayer, referenced 5.10.

The multi-link gateway, referenced 5.2, will also present the samearchitecture, the physical layer, referenced 5.24, the link layer,referenced 5.23, the IP layer, referenced 5.22, the TCP layer,referenced 5.21 and the application layer, referenced 5.20. However, thegateway possesses a management module of the multi-link in itsapplication layer, whereas a management module of the tunnels,referenced 5.52, according to the GRE protocol is integrated in the IPlayer. This module integrates, besides the management of the tunnelsitself, the switching module enabling the choice of the tunnel for eachpacket.

As for the multi-link modem, referenced 5.3, it possesses severalphysical layers referenced 5.341, 5.342 and 5.343. These physical layersare controlled by as many link layers referenced 5.331, 5.332 and 5.333.These different interfaces comprise a first interface, 5.333 and 5.343,of connection of the multi-link modem with the local network. The otherinterfaces corresponding to the different links between the modem andthe remote network, referenced 5.5, here the Internet. The IP layer,referenced 5.32, contains the management module of the GRE tunnelsreferenced 5.62. Here also, this module integrates the dynamic switchingmodule of the tunnel to be used on a packet base. As standard, there isthe TCP layer, referenced 5.31, as well as the application layer 5.30containing the control software of the multi-link.

The role of the control modules of the multi-link will be to carry outthe initialization phase that has already been described as well as thefollow-up of the multi-link. This follow-up will include the dynamicadaptation of the withdrawals and additions of links as well as theexchange of parameters or measurements of performance of each link insuch a manner as to enable the dynamic choice of the link used by eachswitching module.

The choice made for the embodiment of the invention consists in theencapsulation of Ethernet type MAC level packets in the IP tunnelsaccording to GRE. It is possible to realise the invention by remainingat the IP level and using other tunnel techniques. In the embodiment ofthe invention the multi-link emulates an Ethernet connection between thegateway and the modem. This emulation translates into the creationwithin the GRE module, both of the gateway as well as the modem, of avirtual Ethernet interface corresponding to the multi-link. Moreover,the establishment of the multi-link, in a comparable manner to theestablishment of a connection over a link, will allocate a virtual IPaddress to the modem. The modem is therefore in a position to manage anIP address translation step (NAT) to mask the local network with respectto the remote network. Another option would consist in allocating asmany addresses as machines over the local network, but this solution isnot preferred owing to its consumption of addresses. The gatewaytherefore functions as an access server to the network by allocating IPaddresses from its own addressing space to the multi-link modemsestablishing a connection with it.

The details of an exchange of messages between a client of the localnetwork and a server on the remote network will now be described withreference to FIG. 6. The client issues a query referenced 6.1. Thisquery is an IP packet having as source address the IP address of theclient over the local network @IPC and as destination address the IPaddress of the server on the remote network @IPS. Since the multi-linkmodem has been declared as gateway to the remote network, the packet isrouted to it. On the modem, a first address translation phase is carriedout, the source address of the packet is replaced by the virtual IPaddress @IPMV allocated to the modem at the time of the initializationof the multi-link. The modem stores the address of the client at theorigin of the query. The packet is then processed by the GRE module.This module encapsulates the packet in an Ethernet packet, referenced6.2, whose source and destination addresses are the addresses of thevirtual Ethernet interfaces of the modem and the gateway @MACMV and@MACPV. This Ethernet packet is itself encapsulated in an IP packetaccording to GRE, referenced 6.3. It is here that the choice of thetunnel occurs. Depending on the tunnel chosen, the source IP address ofthe packet will be the IP address allocated to the modem at the time ofestablishing the link corresponding to this tunnel. The illustratedembodiment uses the first tunnel, the source address is therefore the IPaddress of the modem allocated by the first access provider @IPM1, thedestination address is the address of the gateway @IPP. This packet isthen processed by the interface corresponding to the tunnel chosen androuted to the gateway. The latter, decapsulates the packet, referenced6.4, and routes it to the server. The response of the server, referenced6.5, and meant for the virtual address @IPMV allocated by the gateway isrouted to its destination via the gateway. This carries out the Ethernetencapsulation resulting in the packet referenced 6.6. Here, once againintervenes the choice of the tunnel that the response will take. Theembodiment illustrates the choice of the second tunnel, the Ethernetpacket will therefore be encapsulated in a GRE packet whose destinationaddress is the address @IPM2, the address of the modem allocated by thesecond access provider and the source address is the address @IPP of thegateway. This IP packet will therefore be routed via the remote networkto the second provider to arrive at the modem via the second access. Onthe modem the packet will be decapsulated, the destination address ofthe client will be restored as the destination address in accordancewith the address translation protocol (NAT) and routed to the client.Hence, this means that the client and the server can communicate via themulti-link as if it involved a single connection linking the localnetwork and the remote network. The modem as well as the gateway is freeto route each packet equally via the different accesses constituting themulti-link. The path taken by a query does not determine the path of theresponse to this query. This connection established between the modemand the gateway will be used in a transparent manner by the applicationsoperating on the client and connecting with the appliances of the remotenetwork. In fact, the applications will communicate normally and openconnections without having to be modified. Everything happens for theseapplications as if the connection were a standard single connectionlinking the local network to the remote network. This remains true inthe case wherein the local network is reduced to the single clientappliance directly integrating the multi-link modem functionality.

In this manner, through a judicious tunnel choice policy, it is possibleto make full use of the different connections between the local networkand the remote network. This choice policy can be based on a statisticaldistribution taking account of the different bandwidths of the links.However, it is also possible to dynamically collect statistics on therate of use of the links for determining this choice. In this case, themodem and the gateway share the information on the links via the controlconnection. Different parameters can be retained for this choice, suchas the error rate, the travelling time, the bandwidth, etc. It is alsopossible to privilege certain links for certain types of traffic, aschoosing a link having a low travelling time for voice and a link havinga high bandwidth for video. It is also possible to take into accounteconomic criteria in the choice policy, particularly if certain linksoffer tariffs as per the quantity of data passing through the link.

The packets exchanged via several links can lose their initial sequenceorder, particularly if the different links have different latency times.Even though rescheduling is managed by the higher protocol layers suchas TCP, it may be interesting to carry it out at this level. Toaccomplish this, it is possible to use a GRE option for adding asequence number enabling the sequence to be recomposed.

The embodiment illustrates a tunnel technique, GRE, and the emulation ofan Ethernet link in the tunnel. It is obvious persons skilled in the artthat it is possible to use any other tunnel creation technique and thatother choices of the encapsulated layer in the tunnel are possible. Inparticular, it is possible to encapsulate the IP packets directlywithout going through an Ethernet packet.

Naturally, the invention is not restricted to the previously describedembodiments.

In particular, the embodiment illustrates the case of a modem linking alocal network to a remote network and being used for relaying thepackets between one or more clients of the local network and appliances,typically server, of the remote network. It is obvious that, accordingto the invention, the local network can be reduced to an appliancecalled modem, which is then integrated to a single client wishing tocommunicate with the remote network.

The invention claimed is:
 1. Method of establishing a multi-link connection between a local communication network through digital data packets, said local communication network comprising a multi-link modem, and a remote network, said remote network comprising a multi-link gateway, wherein the method comprises the following steps: opening of a connection for each interface of the multi-link modem with the remote network; establishing of a control link over any of said opened connections, said control link being dedicated to exchanges between the multi-link modem and the multi-link gateway, for controlling the function of the multi-link connection through transmission of information shared over said control link between said multi-link modem and said multi-link gateway to a dynamic switching module for choosing a tunnel used for relaying packets, said control link being established between said multi-link modem and said multi-link gateway, for each of the connections thus opened, establishment of a corresponding communication tunnel between the multi-link modem and said multi-link gateway using the said connections, and for each digital data packet exchanged between the local network and the remote network, both through the modem as well as the gateway, a choice of the tunnel used for routing the packet in a transparent manner for the applications using the multi-link connection, said choice being based on said information shared between said multi-link modem and said multi-link gateway over said control link.
 2. Method according to claim 1, wherein it comprises furthermore of an allocation step of virtual address to the multi-link modem by the multi-link gateway.
 3. Method according to claim 1, wherein said controlling the function of the multi-link via said control link between the multi-link modem and the multi-link gateway comprising a dynamic adaptation to withdrawals and additions of connections between said multi-link modem and said multi-link gateway.
 4. Method according to claim 1, wherein the choice step is carried out according to parameters specific to each tunnel.
 5. Method according to claim 4, wherein the parameters specific to each tunnel used in the choice step include the instantaneous usage rate of each connection.
 6. Multi-link communication appliance for establishing a multi-link connection between a local communication network through digital data packets, said local communication network comprising said multi-link communication appliance, and a remote network, said remote network comprising a multi-link gateway, said multi-link communication appliance comprising a plurality of means of opening connections between the local network and the remote network, wherein it further comprises: interfaces for opening connections between itself and the remote network, a control module for establishing of a control link over any of said opened connections, and for controlling the function of the multi-link using said control link, said control link being dedicated to exchanges between the multi-link modem and the multi-link gateway, for controlling the function of the multi-link connection through transmission of information shared over said control link between said multi-link modem and said multi-link gateway to a dynamic switching module for choosing a tunnel used for relaying packets, said control link being established between said multi-link communication appliance and said multi-link gateway, for each of the connections thus opened, a management module for establishing a corresponding communication tunnel between itself and said multi-link gateway using the said connection, and for each digital data packet that it relays between the local network and the remote network, a dynamic switching module for choosing of the tunnel used for relaying the said packet, said choice being based on said information shared between said multi-link modem and said multi-link gateway over said control link.
 7. Appliance according to claim 6, wherein the control module further allows for a dynamic adaptation to withdrawals and additions of connections between said multi-link communication appliance and said multi-link gateway.
 8. Multi-link data packet relay appliance that can be connected to a communication network through digital data packets over a multi-link connection, wherein it comprises a control module for establishing of a control link over said multi-link connection, and for controlling the function of the multi-link connection using said control link, said control link being dedicated to exchanges between said multi-link data packet relay appliance and a second multi-link data packet relay appliance giving access to a second communication network, for controlling the function of the multi-link connection through transmission of information shared over said control link between said multi-link modem and said multi-link gateway to a dynamic switching module for choosing a tunnel used for relaying packets, said control link being established between said multi-link communication appliance and said second multi-link data packet relay appliance, said controlling function of said control module choosing a tunnel for routing of a packet over said multi-link connection.
 9. Appliance according to claim 8, wherein said control module further controls dynamic adaptation to withdrawals and additions of connections between said multi-link data packet relay appliance and said second multi-link data packet relay appliance. 